Karst caves exhibit a wide range of hydrological and hydrochemical responses to infiltration events, due to their physical heterogeneity in space and dynamic variability over time, and due to non-Gaussian inputs (rain) and outputs (discharge). This paper reviews different approaches of studying seepage water in caves, in order to understand the infiltration regimen in the non-saturated zone of karst areas. As an illustration, we describe a four-year study of the active carbonate-water system in the Cueva del Agua (Granada, southern Spain) that automatically logs the discharge from a stalactite. The results indicate that: (1) the drip water regime is not seasonal, but is linked instead to slow infiltration. Sudden changes in drip water regime occur due to infiltration along preferential flow paths and the draining of water of supersaturated water from reserves in the microfissure and pore system; (2) the drip rate is not linear over time. When dripping is constant, barometric oscillation of the air is the principal factor causing a chaotic a drip flow regime. Over a short period of two to three days, a mean variation in air pressure inside the cave of 10 (±3.7) mbar causes a mean oscillation in the drip rate of 0.5 (±0.2) mm/h. The increase in air pressure translates into an increase in the relative thickness of the gaseous phase of the drip water at the cost of the aqueous phase, so leading to a reduction in the drip rate from the stalactite.
Fernandez-Cortes, Angel; Jose Maria Calaforra; and Francisco Sánchez-Martos.
Hydrogeochemical processes as environmental indicators in drip water: study of the Cueva del Agua (Southern Spain).
International Journal of Speleology,
Available at: http://scholarcommons.usf.edu/ijs/vol37/iss1/4